The present invention relates to a process for producing catalysts for synthesis of unsaturated aldehydes and unsaturated carboxylic acids, namely, catalysts used for synthesis of acrolein and acrylic acid or methacrolein and methacrylic acid by gas phase catalytic oxidation of propylene, isobutylene or tertiary butanol with molecular oxygen.
Hitherto, many processes have been proposed for production of catalysts used for synthesis of unsaturated aldehydes and unsaturated carboxylic acids. In the case of using isobutylene or tertiary butanol as a starting material, many catalysts used for preparation of methacrolein and methacrylic acid by gas phase catalytic oxidation of isobutylene or tertiary butanol at high temperatures are proposed, for example, in Japanese Patent Kokai (Laid-Open) Nos.57-130949, 58-121236, 59-31727, 60-28824 and 63-66141. However, most of these proposals concern with the kinds of the elements which constitute the catalysts and the ratios of the elements. Some of them disclose processes of calcinating a catalyst precursor at a temperature within a specific range in the course of preparation of the catalyst, but none of them refer to calcinate the precursor in an atmosphere of a specific gas composition. Besides, the catalysts obtained by these processes have not yet reached the sufficient level as industrial catalysts. Further improvements are demanded from the industrial view point of catalyst performances such as catalytic activity and selectivity for the desired products.